Leukocyte trafficking to the skin is directed in part by the adhesive interactions between the vascular endothelial adhesion molecule E- selectin and carbohydrate ligands on leukocytes. The presence of the carbohydrate epitope, cutaneous lymphocyte antigen (CLA), on PSGL-1 expressed on skin-homing T-lymphocytes, is directly correlated with E- selectin ligand activity. Recent data from our laboratory suggest that several glycoproteins bearing CLA exist on the human myeloleukemia cell line KG1a. We hypothesize that these structures mediate leukocyte migration to the skin. The main objectives of this research project are to (1) identify and define the glycoproteins bearing CLA on KG1a membrane, (2) characterize their ability to function as E-selectin ligands, and (3) analyze their expression on malignant leukocytes. This project will employ a new and innovative method for identifying molecules that mediate adhesive interactions under physiologic shear flow conditions. This novel adhesion assay system allows for direct, real-time observation of adhesive interactions between cells and immobilized substrates blotted onto PVDF membranes. We plan on preparing plasma membrane fractions of KG1a cells, resolving the constituent proteins by SDS-PAGE and Western blotting. After immunostaining CLA+ glycoproteins with moAb HECA-452, we will analyze the E-selectin ligand activities of these distinct glycoproteins. This study will uncover molecules expressed by myeloid cells that may mediate their migration to the skin as well as other tissues and will provide molecular targets for developing therapies that control pathologic states distinguished by leukocyte skin infiltration.